RM0312 datasheet(182/275 Pages) STMICROELECTRONICS

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Inter-integrated circuit (I2C) interface

RM0312

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DocID022352 Rev 3

19.4.3

Error conditions

The following are the error conditions which may cause communication to fail.

Bus error (BERR)

This error occurs when the I2C interface detects an external stop or a start condition during

an address or data transfer. In this case:

•

The BERR bit is set and an interrupt is generated if the ITERREN bit is set

•

In the case of the slave: data are discarded and the lines are released by hardware:

–

In the case of a misplaced start, the slave considers it is a restart and waits for an

address or a stop condition.

–

In the case of a misplaced stop, the slave reacts in the same way as for a stop

condition and the lines are released by hardware.

•

In the case of the master: the lines are not released and there is no effect in the state of

the current transmission: software can decide if it wants to abort the current

transmission or not.

Acknowledge failure (AF)

This error occurs when the interface detects a non-acknowledge bit. In this case,

•

The AF bit is set and an interrupt is generated if the ITERREN bit is set

•

A transmitter which receives a NACK must reset the communication:

–

If slave: Lines are released by hardware

–

If master: A stop condition or repeated start must be generated by software

Arbitration lost (ARLO)

This error occurs when the I2C interface detects an arbitration lost condition. In this case,

•

The ARLO bit is set by hardware (and an interrupt is generated if the ITERREN bit is

set).

•

The I2C interface goes automatically back to slave mode (the MSL bit is cleared)

•

When the I²C loses the arbitration, it is not able to acknowledge its slave address in the

same transfer, but it can acknowledge it after a repeated start from the master.

•

Lines are released by hardware

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